Device for adjusting the focal point of a photographic lens

ABSTRACT

In a device for adjusting the focal point of a photographic lens which comprises a reception cylinder, a rotatable cylinder and a lens holding cylinder, the rotatable cylinder has an annular groove formed peripherally thereof and engageable with sloped surfaces formed on anti-slip members. The anti-slip members are adjustable to a position for smoothly rotating the rotatable cylinder within the reception cylinder.

ilnite tates atet Ito et all. 1 Jan. 22, 1974 [54] DEVICE FOR ADJUSTING THE FOCAL 2,461,357 2/1949 Broido et al. 350/257 POINT OF A PHOTOGRAPH: LENS 2,017,823 10/1935 Taylor 350/257 2,732,776 1/1956 Meixner.... 350/255 1 Inventors: Tadashl Kanehlm sorlmachl, 2,383,439 8/1945 Baer 350/252 both 0f Japan FOREIGN PATENTS OR APPLICATIONS [73] Assignw Kabushiki Kaisha, Tokyo 309,938 1929 Great Britain 350/257 Japan [22] Filed; 1 197 Primary Examiner-David Schonberg Assistant Examiner-Michael J. Tokar [21] Appl' 208,610 Attorney, Agent, or Firm-William R. Woodward [30] Foreign Application Priority Data [5 ABSTRACT Dec. 23, 1970 Japan 45/129046 In a device for adjusting the focal point of a photographic lens which comprises a reception cylinder, at [52] US. Cl 350/252, 350/245, 350/257 rotatable cylinder and a lens holding cylinder, the ro- [51] Int. Cl. G02b 7/02 tatable cylinder has an annular groove formed periph- [58] Field of Search 350/245-257 erally thereof and engageable with sloped surfaces formed on anti-slip members. The anti-slip members [56] References Cited are adjustable to a position for smoothly rotating the UNITED STATES PATENTS rotatable cylinder within the reception cylinder.

2,067,189 1/1937 Howell 350/257 1 Claim, 3 Drawing Figures PATENTEB JANZZIBH FIG. 2

FIG. l

TADASHI ITO KANEHIRO \SORIMACH'I IN VENTORS A TTOR NEY DEVICE FOR ADJUSTING THE FOCAL POINT OF A PHOTOGRAPHIC LENS BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to a device for adjusting the focal point of a photographic lens, and more particularly to improvements in the rotatable cylinder holding mechanism in such a device which comprises a rotatable cylinder received in a reception cylinder secured to a camera and a lens holding cylinder screwed for axial movement in the rotatable cylinder.

2. Description of the Prior Art In a photographic lens of the described type, the presence of any axial clearance between the reception cylinder and therotatable cylinder may result in an unstable position of the lens with respect to the surface of a photographic film and accordingly in an error of focusing. Also, the absence of a proper clearance between the two cylinders may cause unsmoothness f the focusing operation.

Heretofore, in assembling a photographic lens of such construction, a washer has been employed to adjust the clearance between the rotatable cylinder and the reception cylinder so as to eliminate any axial clearance and permit smooth rotation of the rotatable ring. However, this has required much time and high cost.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a photographic lens of very much simplified construction which eliminates all the foregoing disadvantages existing in the prior art.

Such object may be achieved by providing a device for adjusting the focal point of a photographic lens which comprises a reception cylinder secured to a camera body, a rotatable cylinder received in the reception cylinder and rotatable with an operating ring but limited in axial movement, and a lens holding cylinder holding therein a lens system and screwed in the rotatable cylinder for linear axial movement. The rotatable cylinder has an annular groove formed peripherally thereof for receiving a pair of anti-slip members secured to the reception cylinder. The anti-slip members each have a surface portion sloped with respect to the optical axis of the lens system and engageable with the groove on the rotatable cylinder to thereby limit axial movement of the rotatable cylinder. Each of the antislip members is provided by a portion of a ring having an arcuate inner edge extending along the groove on the rotatable cylinder. Each of the anti-slip members has two parallel slots through which it is secured to the reception cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS Various embodiments of the present invention will be described in detail by reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal sectional view of a photographic lens assembly according to the present invention;

FIG. 2 is a rear end view of the photographic lens assembly; and

FIG. 3 is a enlarged, fragmentary sectional view showing various forms of the anti-slip mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. I and 2, a camera body 1 has a reception cylinder 2 integrally attached thereto and formed with a flanged portion 2, for attaching the cylinder 2 to the camera body as by screws or other suitable means. An internally threaded cylinder 3 is rotatably received in the reception cylinder 2, and an externally threaded lens holding cylinder 4 is screwed into the internally threaded rotatable cylinder 3.

The lens holding cylinder 4 has a shutter casing 9 fixed to one end thereof by means of nuts 10. The shutter casing 9 houses therein a lens system 6, shutter blade 7 and a stop blade 8. The lens holding cylinder 4 is formed with a pair of guide grooves 11 for linear advance, each adapted to receive a pin 12 studded in a fixed portion of the camera body.

The rotatable cylinder 3 has an annular groove 3, formed peripherally of the rear or left end portion thereof. A pair of anti-slip members 14 is attached to the rear or left end face of the reception cylinder 2 by means of screws 15 passing through adjust slots 14, formed in the anti-slip members '14, so that one end 14, of each member 14 is engaged with the annular groove 3, to prevent the rotatable cylinder 3 from forwardly slipping out of the reception cylinder 2.

An operating ring 13 is secured to the flange 3 of the rotatable cylinder 3. In the embodiment illustrated herein, this ring also serves as a protective cover for the shutter casing 9.

The rotatable cylinder 3 is rotatable with rotation of the operating ring 13 so that the lens holding cylinder 4 in threaded engagement with the cylinder 3 may be linearly guided with the aid of the guide grooves 11 and pins 12 to thereby accomplish a focusing operation through such axial movement without any accompanying rotational movement.

The end 14, of each anti-slip member 14 and the rear edge of the groove 31, on the rotatable cylinder 3 are both shown as being sloped in the embodiment of FIGS. 1 and 3, but either the anti-slip members 14 or the groove 3, may have such a sloped surface portion, as shown in FIGS. 4 and 5.

Attachment of the anti-slip members 14 to the reception cylinder 2 may be accomplished by first loosely fitting the former to the latter by means of screws 15 and then forcing the anti-slip members 14 in the direction toward the lens center as indicated by arrow a (FIGS.

3 to 5) so as to insert the end 14, into the groove 3,. When the end 14, of each anti-slip member 14 is engaged with the rear edge 3 of the groove 3,, the sloped surface portion(s) formed in both or either of the members 14 groove 3, permits the rotatable cylinder 3 to be forced in the direction as indicated by arrow b, thereby bringing the flange surface 3 of the cylinder 3 into contact with the forward end face 2, of the reception cylinder 2. When a position in which no axial clearance is present is reached, with smooth rotation of the rotatable cylinder 3 relative to the reception cylinder 2, the anti-slip members 14 may be tightly fastened by the screws 15 to complete the adjustment.

As will be appreciated from the foregoing description, the present invention provides a construction in which the clearance between the rotatable cylinder and the reception cylinder may be adjusted by the anti-slip members for the rotatable cylinder, and this leads to the provision of a camera which does not require so much time for assembly and adjustment as experienced with conventional cameras and which permits the for cusing operation to be achieved smoothly and readily without causing any error during the focusing.

We claim:

1. A device for adjusting the focal point of a photographic lens comprising:

a reception cylinder secured to a camera body;

a rotatable cylinder received in said reception cylinder and rotatable together with an operating ring but limited in axial movement, said rotatable cylinder having an annular groove which is formed peripherally thereof for receiving a pair of anti-slip members affixed to said reception cylinder and which has a side wall having conical surface, each of said anti-slip members being provided by a portion of a ring having an arcuate inner edge extending along said groove on said rotatably cylinder, and having a conical surface engageable with said conical surface of the rotatable cylinder and parallel slots through which each of said anti-slip members is secured to said reception cylinder in a position such as to provide a rotation bearing for said rotatable cylinder and to maintain a rotation-aiding clearance between said reception cylinder and said rotatable cylinder, while limiting axial movement of said rotatable cylinder;

and a lens holding cylinder holding therein a lens system and screwed in said rotatable cylinder for linear axial movement in response to the rotation of said rotatable cylinder.

-UNITE D. STATES PATENT OFFICE CERTIFICATE OF CORRECTION I Patent No. 3,73 Dated January .2 1974 Inv or Tadashi ITO and Kanehiro SORIMACHI It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I In Column- 1, line 67, after "showing" delete "various forms of".

In comm; 2, line $27-55, after "3" in line 43, insert a period and .delete but either the anti-slip members I '14 or" and delete everything down to the end of line 45. vIn Column 2, line 49-, change "FIGS." to FIG.

g In Column 2, line 50 after the first occurrence of "3", deleteQ'-'to 5".

In Column 2, line 53, change "portion(s)" to portions-- end delete-"or either of". v I

In Co1u mn2, line 54, after "14" insert and end after the. first occurrence of "3" change "permits" to cause i I Signed lahd--sea1ed this 14th day of January 1975. g

(SEAL) Attest: I

McCOY M'. IGIBSONJR; I c; MARSHALL 1mm Attesting Officer Commissioner of Patents FORM P0-1050 (10-69) y Y Q uscoMM-oc suave-pen R ".5. GOVERNMENT PRINTING OFFICE i969 0-366-33L 

1. A device for adjusting the focal point of a photographic lens comprising: a reception cylinder secured to a camera body; a rotatable cylinder received in said reception cylinder and rotatable together with an Operating ring but limited in axial movement, said rotatable cylinder having an annular groove which is formed peripherally thereof for receiving a pair of anti-slip members affixed to said reception cylinder and which has a side wall having conical surface, each of said anti-slip members being provided by a portion of a ring having an arcuate inner edge extending along said groove on said rotatably cylinder, and having a conical surface engageable with said conical surface of the rotatable cylinder and parallel slots through which each of said anti-slip members is secured to said reception cylinder in a position such as to provide a rotation bearing for said rotatable cylinder and to maintain a rotationaiding clearance between said reception cylinder and said rotatable cylinder, while limiting axial movement of said rotatable cylinder; and a lens holding cylinder holding therein a lens system and screwed in said rotatable cylinder for linear axial movement in response to the rotation of said rotatable cylinder. 